The epidemiology of arboviruses of public health importance in Ohio is being investigated through a program of surveillance and research. Surveillance of human cases of St. Louis and California encephalitis is maintained by contacting all physicians reporting encephalitis or meningitis infections and requesting acute and convalescent sera from these patients for serologic testing. Epidemiological and clinical data are gathered and analyzed for any case having a confirmed or presumptive diagnosis of arthropod borne encephalitis. Surveillance of arbovirus activity is done by virus isolation from vectors and vertebrate sera and antibody testing of vertebrate sera. Collections are made biweekly in order to detect evidence of or increases in arbovirus activity in time to institute preventive measures. Research includes: surveys to identify vector species and through virus isolation, arboviruses occurring in Ohio; field and laboratory investigations of vector potential (transmission-infectivity characteristics, transovarial transmission); vector ecology to determine the biological and behavioral characteristics which play a role in arbovirus epidemiology; serologic and virologic studies of wild vertebrates to establish the natural arbovirus reservoirs; and vector control investigations, principally through detection of diseased vectors, laboratory culture and studies on the pathogenicity of biological agents of potential use in control.